Question

Why is it beneficial that many predatory fish have larval and juvenile stages that feed at a low trophic level, while the adults feed at a tertiary or quaternary trophic level?

Answer 1

I think it probably has to do with natural selection. Only the strongest members of the species survive the larval stage. Weak/poorly adapted larva with bad genes get eaten. So that way, more resources are available for stronger members of the species and the weak/poorly adapted genes aren't passed on.